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  • Phototaxis  (13)
  • Blue-green algae  (7)
  • Life and Medical Sciences  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Role of three basic light reactions in photomovement of desmids (1977)
    Springer
    Planta 137 (1977), S. 207-214 
    Details
    ISSN: 1432-2048
    Keywords: Desmids ; Light trap method ; Microcinematography ; Photokinesis ; Photophobic reaction ; Phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoaccumulations in light trap experiments have been studied in the desmids, Cosmarium, Micrasterias and Euastrum. Dependence of accumulation density on exposure time follows saturation curves, while dose response curves show optima. Time-lapse microcinematography and population methods have revealed that all three basic light-induced motor responses known in microorganisms participate in producing photoaccumulations in desmids. During the initial phase the cells are phototactically attracted towards the trap by scattered light. In low light intensity traps photokinetic reactions may play only a minor role, since photokinesis could be evoked only by light intensities≧100 lx in Cosmarium cucumis. True photophobic reactions have been demonstrated for the first time in desmids. There are two types of phobic responses in desmids: either the cell reverses its movement or it swings sidewise into the new direction. Behaviour of partially shadowed cells suggests that perception of light direction is brough about by simultaneous intensity measurement at two or more sites within the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388152
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  • 2
    Electronic Resource
    Electronic Resource
    Wavelength dependence of photomovement in desmids (1979)
    Springer
    Planta 145 (1979), S. 1-5 
    Details
    ISSN: 1432-2048
    Keywords: Desmids ; Phobic response ; Photoaccumulation ; Photokinesis ; Phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The action spectra of phototaxis, photokinesis, and photophobic response of Cosmarium cucumis, C. botrytis, C. margaritiferum, and Micrasterias denticulata show peaks in the blue (about 440 nm) and red (about 670 nm) spectral regions and thus indicate the involvement of photosynthetic pigments. According to the differences in the action spectra, light-induced movement responses may be linked with photosynthesis in different ways. Results with population methods have been supported by time-lapse microcinematography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379921
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  • 3
    Electronic Resource
    Electronic Resource
    Phototactic attraction in light trap experiments: A mathematical model (1980)
    Springer
    Journal of mathematical biology 10 (1980), S. 257-269 
    Details
    ISSN: 1432-1416
    Keywords: Blue-green algae ; Light trap ; Mathematical model ; Phobic response ; Phormidium uncinatum ; Photoaccumulation ; Photomovement ; Phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A mathematical model has been developed to evaluate the contribution of phototactic responses in light-induced accumulations. A set of differential equations describes the organism density inside and outside of the light trap as well as on its border. The model predicts that organisms first occupy the rim of the light trap and then gradually fill the interior. This has been substantiated experimentally. Computer simulations of light-induced accumulations in a light trap agree with the measured values. The distance from the trap within which organisms respond phototactically depends on the organism density, which determines the amount of stray light, and on the zero threshold for both phototaxis and photophobic response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276985
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  • 4
    Electronic Resource
    Electronic Resource
    Simultaneous tracking of flagellates in real time by image analysis (1991)
    Springer
    Journal of mathematical biology 30 (1991), S. 63-72 
    Details
    ISSN: 1432-1416
    Keywords: Chain coding ; Gravitaxis ; Image analysis ; Peridinium gatunense ; Phototaxis ; Velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The hardware and software components are described to track many flagellates simultaneously in real time. The technique is based on on-line digitization of four frames taken at 80 ms intervals and stored in a specialized video memory. The outline and position of each organism are determined by chain coding and followed through the recorded series of images. The movement vectors of all organisms tracked are stored in the form of deviation angles from a predefined stimulus (light or gravity) direction and the distance each organism has moved in the time interval determined by the hardware clock of the computer. Subsequent programs allow one to determine circular histograms of movement directions and velocities in dependence of the movement direction. Examples of several orientation patterns are given for both photoorientation and gravitaxis in the dinoflagellate, Peridinium gatunense.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00168007
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  • 5
    Electronic Resource
    Electronic Resource
    Participation of two photosystems in the photo-phobotaxis ofPhormidium uncinatum (1974)
    Springer
    Archives of microbiology 96 (1974), S. 255-266 
    Details
    ISSN: 1432-072X
    Keywords: Cyanophyceae ; Phototaxis ; Phobotaxis ; Photosynthesis ; Electron Transport Chain ; Inhibitors ; Action Spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. A hypothesis based on the Hill-Bendall-model of photosynthetic electron transport is proposed to explain positive and negative photo-phobotaxis inPhormidium uncinatum. In the non-cyclic electron chain a pool is located into which photosystem II (e. g. by absorption by C-phycoerythrin, 561 nm) feeds electrons while photosystem I (e.g. 723 nm) drains electrons out of it. 2. Interruption of the electron flow into the pool causes a sudden decrease of the pool size and thus a positive phobic response. This happens e.g. when an organism leaves a trap which is illuminated by a wavelength absorbed by photosystem II pigments (e. g. 561 nm). 3. A negative reaction takes place when electrons are suddenly drained out of the pool; again the pool size decreases. This is the case when an organism enters a light trap illuminated by photosystem I light (723 nm). 4. The net flow of electrons into or out of the pool—and thus the reaction sense—can be manipulated by the relative excitation of the two photosystems or by blocking the electron influx by DCMU.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00590181
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  • 6
    Electronic Resource
    Electronic Resource
    Further evidence for the electron pool hypothesis (1976)
    Springer
    Archives of microbiology 110 (1976), S. 301-303 
    Details
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Electron pool hypothesis ; Photophobic reaction ; Photosystems ; Phormidium uncinatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In continuation of experiments with photo-system II inhibitors [3-(3,4-dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6-isopropylbenzoquinone] the effect of photosystem I inhibitors was studied. 1. Neither the plastocyanin inhibitor, potassium cyanide, nor the ferredoxin antagonist, disalicyliden propandiamin, markedly affected those phobic reactions which are mediated by the electron transport via photosystem II into the electron pool. 2. On the other hand those phobic reactions, which are triggered by an increased flow of electrons out of the pool, are specifically inhibited by both substances. These results are regarded as further evidence that there is only one electron pool, the level of which triggers photophobic reactions and is located in the linear electron transport chain near photosystem II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690242
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  • 7
    Electronic Resource
    Electronic Resource
    Evidence of electrical potential changes in photophobically reacting blue-green algae (1978)
    Springer
    Archives of microbiology 118 (1978), S. 115-119 
    Details
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Light-induced potential changes ; Phormidium uncinatum ; Photophobic response ; Sensory transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The correlation between photophobic responses and light-induced electric potential changes has been studied in the blue-green alga Phormidium uncinatum. 1. The photophobic reaction time depends on both length of preillumination and presentation time of stimulus. Under optimal conditions a reaction time of about 10 s has been determined. 2. Light-induced potential changes can be measured by means of external electrodes with a small gap between them bridged by a population of perpendicularly oriented trichomes. These potential changes follow a light-dark cycle with a lag phase of about 10 s. 3. The amplitude of these light-induced potential changes increases with light intensity until it reaches a saturation value of about 12 mV at 10000 lx. The action spectrum resembles the photophobic action spectrum with peaks in the absorption region of C-phycoerythrin and chlorophyll a. The significance of light-induced potential changes as a means of sensory transduction for photophobic responses in blue-green algae is being discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00406083
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of inhibitors on photomovement in desmids (1981)
    Springer
    Archives of microbiology 129 (1981), S. 168-172 
    Details
    ISSN: 1432-072X
    Keywords: Desmids ; Inhibitors ; Microvideography ; Photokinesis ; Photophobic response ; Photosynthetic electron transport ; Phototaxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of the inhibitors of the photosynthetic electron transport chain, 3-(3′,4′-dichlorophenyl) 1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), on the three phtoomovement responses known in the desmid Cosmarium cucumis have been studied. Both inhibitors block photokinesis very effectively in their respective specific concentration range. Most of the impairment of phototaxis and the photophobic response observed in population techniques seems to be due to a reduced motility of the cells, since microvideographic analysis of the cell movement indicated that the inhibitors do not affect the phobic response at all and that there is only partial inhibition of phototaxis. Both the fraction of motile cells and the duration of motility periods are affected by the inhibitors. The results demonstrate that, though all three photoresponses are mediated by chlorophyll acting as photoreceptor, at least the phobic response is independent of the photosynthetic electron transport chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00455356
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  • 9
    Electronic Resource
    Electronic Resource
    Phototaxis in the gliding flagellate, Euglena mutabilis (1983)
    Springer
    Archives of microbiology 135 (1983), S. 25-29 
    Details
    ISSN: 1432-072X
    Keywords: Electron microscopy ; Euglena mutabilis ; Flagellate ; Photomovement ; Photoreceptor ; Phototaxis ; Single-cell analysis ; Videomicroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Due to the lack of an emergent flagellum the green flagellate Euglena mutabilis is restricted to gliding motility. During forward movement, the organisms orient positive phototactically in the presence of a suitable light stimulus. The cell contains both a stigma and a paraflagellar body which differ in shape and size from the organelles found in E. gracilis. The degree of orientation in white light follows an optimum curve with a maximum at about 100 lx. The spectral sensitivity shows a number of prominent peaks in the blue and green regions and extends well into the red region of the visible spectrum. Since the cell does not rotate during locomotion a periodic shading mechanism cannot account for phototactic orientation. Thus, phototaxis in the related species, E. gracilis and E. mutabilis differ in their photoreceptor molecules, their sensory transduction chains and their strategies of light direction detection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00419477
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  • 10
    Electronic Resource
    Electronic Resource
    Phototaxis in the flagellates, Euglena gracilis and Ochromonas danica (1981)
    Springer
    Archives of microbiology 130 (1981), S. 78-82 
    Details
    ISSN: 1432-072X
    Keywords: Euglena ; Flagellates ; Microvideography ; Ochromonas ; Photomovement ; Phototaxis ; Statistical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oriented movement with respect to laterally impinging white light of the flagellates Euglena gracilis and Ochromonas danica has been analyzed in an individual cell study with a microvideographic technique. Using the deviation of track segments (in given time intervals of 1 s) from the light direction as raw data allowed a computer based analysis of the direction distribution. A number of statistical methods employed to test the significance of the obtained results demonstrated an obvious phototactic orientation in Ochromonas which was positive (toward the light source) in low illuminance (1.25 lx=5.3×10-3 Wm-2) and negative in higher illuminance (〉12.5 lx=5.3×10-2 Wm-2). Since in this flagellate the threshold for negative phototaxis is much lower than that for the step-up photophobic response, the hypothesis that negative phototaxis may be brought about by repetitive step-up phobic responses can be rejected for at least this organism. In Euglena positive phototaxis was observed in ≤50 lx (=0.21 Wm-2), while an illuminance of 500 lx (=2.1 Wm-2) caused a negative phototaxis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527076
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